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Old 05-28-2019, 12:29 PM   #26
dbarton
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Quote:
Originally Posted by Texas240 View Post
It does make difference. Im still using the mustang master on the stock 240 calipers. R calipers did brake better except the squeal was horrible on my car and turned into a slight grinding sound here and there after the brakes would get warm. But it does make a difference
My question was about the STEPPED bores.
It appears that the Mustang master has the same bore for front and rear ports.
But with Volvo, you have a stepped bore, at least from what I can gather in any MC prior to ABS. Maybe with ABS too.
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From VOLVO: Dual circuit reliability. Volvos have a triangle-split dual circuit braking system, including a stepped-bore master cylinder. This means that if one circuit should fail, both front brakes and one rear will still operate, retaining about 80% braking effect with maximum directional stability.
From an early Greenbook for 1975+ 240:
Master Cylinder (tandem-type, step-bored), 4 cyl., 6 cyl.
Primary bore diameter: 22.3 mm
Secondary bore diameter: 15.75 mm


Does anyone know if going from the stepped Volvo MC to a non-stepped Ford MC makes any difference? Or if you just don't know, will ignoring this matter?
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Old 05-28-2019, 12:32 PM   #27
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Originally Posted by DrZiplok View Post
I haven't looked, sorry. In our case it's actually more interesting for the front / rear bore ratios to look completely non-Volvo as we're attempting to get the EBFD in the ABS to think it's in an E46 M3.

As a datapoint, we did about 15 hours of our last 24-hour race on just the front brakes after breaking a rear caliper bracket. It made late trail braking a bit weird, but didn't seem to affect our lap times or overall enjoyment. So, probably not a huge difference.
Thanks. You posted this as I was composing my above post. That helps a little.
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Old 05-28-2019, 10:36 PM   #28
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I remember having this convo with you before about how the 240 master was stepped but the mustang wasnt.
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Old 05-28-2019, 10:45 PM   #29
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The Mustang MC I bought was over a 1" bore, I bought it from Rockauto, and they had the bores listed. I bought the largest one. I revisited those MC's and most are not listed anymore.. I do not have it here, it's in my huge pile of LS swap parts at my friends shop. I will try to get the p/n this week.

What is the difference between a stepped bore and a non stepped bore?
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Old 05-29-2019, 12:14 AM   #30
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The stepped bore master was developed by Volvo to reduce the pedal travel and pressure required to stop the car in the event of a circuit failure. ABS masters are not stepped.

https://www.jstor.org/stable/4471799...n_tab_contents
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Old 05-29-2019, 08:40 AM   #31
dbarton
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Quote:
Originally Posted by hiperfauto View Post
The stepped bore master was developed by Volvo to reduce the pedal travel and pressure required to stop the car in the event of a circuit failure. ABS masters are not stepped.
So ABS masters are not stepped? Ok, that answers that question.

So then I guess all other 240 masters are Stepped.

Stepped bore means the front circuit has a smaller piston than the rear circuit.
Volvo REAR bore: 22.3 mm
Volvo FRONT bore: 15.75 mm
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Old 05-29-2019, 06:34 PM   #32
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Quote:
Originally Posted by Texas240 View Post
Im still using the mustang master on the stock 240 calipers.
How is it? I'm in need of a master cylinder and will go big brake eventually, so I might just skip to the mustang master on the stock brakes. My car is non-ABS. What is it like with the mustang master and stock brakes?
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Old 05-29-2019, 09:29 PM   #33
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Quote:
Originally Posted by dbarton View Post
Stepped bore means the front circuit has a smaller piston than the rear circuit.
Volvo REAR bore: 22.3 mm
Volvo FRONT bore: 15.75 mm
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Just in case this confuses someone; the "FRONT" bore in this case actuates the rear brakes, and likewise the "REAR" bore the front brakes.
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Old 05-29-2019, 10:39 PM   #34
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Originally Posted by mck1117 View Post
How is it? I'm in need of a master cylinder and will go big brake eventually, so I might just skip to the mustang master on the stock brakes. My car is non-ABS. What is it like with the mustang master and stock brakes?
Harder pedal, a little more effort to brake. Thats about it. Went from V70r front calipers back to stock 240 calipers. Lost about 6-8 pounds going back to stock. Was able to lock up the fronts now I cant with the stock. Was too lazy to switch back to a non abs master so I left it on. Im not complaining.
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Old 05-30-2019, 07:05 AM   #35
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Old 05-30-2019, 08:56 AM   #36
dbarton
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Quote:
Originally Posted by DrZiplok View Post
Just in case this confuses someone; the "FRONT" bore in this case actuates the rear brakes, and likewise the "REAR" bore the front brakes.
If you're referring to NON-ABS, pretty sure you're wrong.
The below diagram is how my '84 242 is from the factory.

Are you referring to ABS brakes? Maybe that's different.
Dave B.
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Old 05-30-2019, 11:13 AM   #37
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Quote:
Originally Posted by dbarton View Post
If you're referring to NON-ABS, pretty sure you're wrong.
The below diagram is how my '84 242 is from the factory.

Are you referring to ABS brakes? Maybe that's different.
Yes, my turn to inject confusion, sorry.
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Old 05-30-2019, 11:54 AM   #38
dbarton
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Ok, cool. I have not yet found a good diagram for 240 ABS brakes, but I did find this Greenbook diagram for 700 brakes. I suspect it's similar to the 240.

EXCEPT: I would kind of expect the fronts to have individual brake lines going to each front caliper, not a "T" as shown here.
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Old 05-31-2019, 01:14 AM   #39
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Quote:
Originally Posted by dbarton View Post
Ok, cool. I have not yet found a good diagram for 240 ABS brakes, but I did find this Greenbook diagram for 700 brakes. I suspect it's similar to the 240.
The ABS-II routing is pretty boring. There are two lines from the master that go to the ABS valve block; one for the fronts (V), one for the rears (H).

There are three lines that come out of the ABS valve block; front right (r), front left (l), rear (h).

Here's a really good shot of the valve body; you can see the front circuit on the left and the rear circuit on the right: https://www.flickr.com/photos/47640483@N04/5154785667/
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